As usual this expansion, will be free to PC gamers and cost Xbox Live players cash. The Sacrifice will also be available for Mac users.

The Sacrifice will be playable with both the original Left 4 Dead game and Left 4 Dead 2, and will fill in the narrative gaps that led up to the events that occur in The Passing. Gamers will be able to steer the story in the direction they desire, choosing which character dies at the end of the episode.

Additionally, the new DLC will allow owners of Left 4 Dead 2 to play the "No Mercy" episode from the original Left 4 Dead game.

Valve also said that a 150-page digital comic will come out in September to further explore the back stories of the original Left 4 Dead characters.